1. Field of the Invention
This invention relates to a semi-solid ink, above all a semi-solid ink to be applied for the heat transfer recording method such as image processor, electronic typewriter, facsimile or various information boards, etc.
2. Related Background Art
Presently, a thermal transferable material, which is laminated with an ink layer on a base film, has been generally employed for a heat transfer recording method, and recording is generally performed by interposing the thermal transferable material between a recording medium such as paper and a thermal head, and heating the thermal transferable material to melt the ink at the heated portion and setting the melted ink onto the recording medium. However, in applying a heat transfer recording method of the above thermal transferable material, there are some complications of a device constitution such as installation of thermal transferable material supply mechanism in a recording device and also running cost is high, since the thermal transferable material cannot be reused, and further, disposal of the thermal transferable material used was cumbersome.
Against the drawbacks as mentioned above, the filmless heat transfer method employing no base film has been proposed, for example, as disclosed in U.S. Pat. No. 4,561,789. In this method, in place of holding ink on base film, semi-solid ink is kept in a recording head having passage holes, said ink is permitted to flow out through passage holes by heating and melting said ink, and the ink is set onto a recording medium such as paper to effect transfer recording, and many advantages are there such as no consumption of base film as compared with conventional heat transfer recording method, and further good energy efficiency, due to direct heating the ink without through film.
FIG. 1 shows an example of a recording head used in the filmless heat transfer recording method as disclosed in U.S. Pat. No. 4,561,789.
As shown in the drawing, the semi-solid ink 23 is kept in the recording head 1. Here, 2 is a housing and 24 is a heat-generater for heating and melting the semi-solid ink. The heat-generater 24 has passage holes 24a for permitting the ink 23 melted by heating to flow out. 9 is a recording paper as a recording medium, 10 is a platen roller for conveying the recording paper 9. On the semi-solid ink 23, a pressure 11 may be applied for the purpose of facilitating flow-out or supply of the ink 23, if desired.
In the above constitution, when heat is generated at the heat-generater 24, the semi-solid ink 23 in the vicinity of said heat-generater is melted and softened to be lowered in viscosity, whereby the melted ink 23a flows out through the above passage holes 24a. In each heat-generater 24 of the recording heads 1 in an arrayed form these passage holes 24a are provided and by applying selectively heat-generating signals on each respective heat-generaters, desired images such as letters or images are formed on the recording paper 9. The temperature during recording is generally made about 40.degree. to 120.degree. C.
The semi-solid ink to be used in such filmless heat transfer recording method is desired to be melted when heated, not to flow out from passage holes before heating and also readily to be supplied. In the prior art, however, the ink melted by heating may sometimes flow out in a large amount through passage holes to cause "fog" or "tailing" on the images formed. On the contrary, also the ink may flow out insufficiently to cause "defect" in the formed images, whereby formed images become unclear.